News from the APA Annual Convention, Aug. 7-Aug. 10, in Washington DC

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Chimps Driven to Distraction

We all know how hard it can be to hold out for a big reward rather than take a smaller reward right now. But while pigeons, rats, monkeys and chimps show the similar behavior when offered food treats, only chimps can learn to distract themselves to sustain their self-control.

In a session called “Worth Waiting For — The Evolutionary and Developmental Foundations of Self-Control,” Michael Beran, PhD, of Georgia State University, described experiments he has conducted with chimps, orangutans and rhesus and capuchin monkeys.

Orangutans could learn to wait about a minute if it meant they’d get a larger food treat, Beran said. But “rhesus monkeys were terrible – they just never got good at this.” And capuchin monkeys also struggled – but they could exert some self-control under certain conditions.

Beran and his colleagues designed an experiment in which capuchin monkeys were presented with two pieces of banana on a turntable, one small that was close to the monkey and a larger one that was farther away. The monkeys could see both pieces and they were able to stick their hands out of the cage to take the food. The monkeys would initially impulsively grab the smaller, closer piece of banana but eventually they learned to wait for the turntable to spin around and present the bigger piece, Beran said — although some capuchins were better at the task than others.

Chimps, on the other hand, could learn to wait almost as long as children. (Remember Walter Mischel’s marshmallow experiments in which preschoolers had to wait to get two marshmallows instead of one now?) Beran created an accumulation test where chimps would get more food treats if they could wait. The food was given to them through a delivery tube that went into their cages.

“All the chimpanzees learned quickly to wait,” he said, but some would touch or pick up the food (or the food delivery tube) but not eat, having learned that they would still get more as long as they didn’t eat anything. That led Beran to theorize that touching the food or tube might be a distraction that enabled them to wait longer. So he devised another experiment where some chimps were given toys to play with, some could not reach the food delivery tube and some were given no distractions and could reach the tube. The chimps with the toys could wait an additional 500 seconds to get the treats.

“I would make a pretty strong case that this is self-distracting,” he said.